Stiffness Optimization for Ballasted-Ballastless Track Transition Zones in High-Speed Railways

In order to reduce the vibration response of high-speed trains in the ballastless-ballasted track transition zone, a vehicle-track-subgrade coupled dynamic finite element computational model was established. The dynamic response characteristics of the vehicle and track structure were studied by considering different structural treatment measures such as adjusting the stiffness of rail pads, and installing concrete transition slabs and ballast bonding. Adjusting the rail pad stiffness, installing concrete transition slabs, and improving ballast bonding significantly influence the overall vertical stiffness of the track, offering the possibility of optimizing the stiffness of the transition zone through these measures. Concrete transition slabs are particularly effective in reducing the vertical vibration response of the train, while ballast bonding increases the track stiffness, requiring a simultaneous reduction in the stiffness of under-sleeper pads to mitigate wheel-rail forces. The length of concrete transition slab needs to be adjusted according to the actual situation due to the excessive length of transition slab that would increase vehicle vibration response. When the smoothness of track in transition zones is poor (such as the presence of track deflection angles), the vibration response of vehicle is mainly affected by track irregularity and the influence of stiffness transition measures on the vibration response of vehicle is relatively limited.